Republican presidential nominee Donald Trump characterized his July fundraising as being the campaign's "best month yet," as two traditionally influential GOP billionaire donors, David and Charles Koch, shunned his bid for the White House.

In two new fundraising solicitations sent to supporters over the weekend, Trump—who pledged during the primaries to self-fund his campaign, but reneged on that promise after securing the GOP nomination—said that his campaign goal had already met a first match goal of $1 million.

Vowing to personally match new contributions made through July 31 up to $2 million, the real estate mogul boasted that his monthly contributions have been the best yet.

"From our hugely successful fundraising push, to the day Mike Pence joined the ticket, to the wonderful Republican National Convention, July has been our best month yet," Trump wrote in an email Sunday, reiterating his campaign pledges to build a wall on the Mexican border and renegotiate trade deals

That said, Trump basically confirmed reports of a rift with the billionaire Koch brothers, whose financial support of conservative-leaning causes have earned them the scorn of liberal-minded politicians. Last week, Politico reported that the men, turned off by Trump's rhetoric and policies, brushed aside efforts to meet with the GOP nominee.

Yet on Saturday, Trump insisted that he, in fact, had spurned the Kochs' entreaties. The real estate mogul dismissed them as little more than political puppet masters just as they were meeting with hundreds of other big money Republican donors at a retreat in Colorado.

At the meeting in Colorado, Charles Koch encouraged donors to not "just focus on politics [or] we're going to continue to lose." He indicated that he wouldn't spend money to boost Trump, or attack the Democratic nominee.

The real estate mogul's public split with the Koch brothers may also be part of a calculated strategy to assemble an electoral coalition Trump believes may carry him to victory in November.

In recent days and with increasing regularity, Trump has made explicit appeals to dejected supporters of Vermont Senator Bernie Sanders, who dropped out of the race for the Democratic nomination against Clinton before endorsing her.

The bad blood between the two opposing camps was reignited last weekend, after Wikileaks exposed a cache of hacked emails that showed Democratic National Committee staffers favoring Clinton, and at some turns coordinating with her campaign during the primaries.

During the Democrats' convention this week, Trump repeatedly denounced the "rigged" process that handed Clinton the nomination, saying Sanders was wrongfully denied the nomination—then blasting him for ultimately backing Clinton.

'Barely keep up'

Both the Democrats and Republicans have concluded the nomination process, culminating in the last two weeks of pomp, circumstance and controversy of the national conventions. With the general election now in full swing, Trump vowed to double his pledged amount for money received through Sunday at midnight.

"Our fundraising department can barely keep up," Trump exclaimed in the email, exhorting his supporters to contribute more. "I am going to personally match your donation today, and every day you donate up to midnight tomorrow, up to $2 million."

With his real estate empire, television appearance and other business ventures, Trump has far more name recognition than a conventional candidate but no discernible voter turnout operation.

In addition to his campaign's cash deficit when compared to Clinton's, political veterans note Trump hasn't yet begun saturating the airwaves in critical battleground states.

On Monday, the candidate is scheduled to make an appearance in Pennsylvania, a critical swing state where some polls show Trump running neck and neck with Clinton.

It was still unclear, however, how much the billionaire real estate mogul had managed to narrow the gap with Clinton.